Morphology of nonmetallic inclusions and mechanical properties of high strength low-alloy structural steels

In recent years, commercial low-alloy structural steels containing medium carbon and variable amounts of chromium, molybdenum and nickel have been used for many engineering components in quenched and tempered conditions. In particular, light-tempered low-alloy steels are needed for aerospace parts that are heat treated to ultrahigh strengths. Most recently, there has been an increased demand for high strength low-alloy structural steels with superior mechanical properties under severely stressed situations. The isotropy regarding these properties has especially been required. One potential solution to this problem is to control the nonmetallic inclusions of the steels. This review describes recent well-organized studies concerning the effect of the morphology of nonmetallic inclusions on the mechanical properties of low-alloy structural steels quenched and tempered at high strength levels.